<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>position</title>
<style>
	div{
		width: 200px;
		height: 200px;
		font-size: 30px;
		text-align: center;
		line-height: 100px;
	}
	.box1{
		background-color: red;
		position: relative;
		top: 50px;
		left: 50px;
		z-index: 0;
	}
	.box2{
		background-color: green;
	}
	.box3
	{
		background-color: yellow;
		margin-top: -50px;
	}
</style>
</head>
<body>
	<div class="box1">box1</div>
	<div class="box2">box2</div>
	<div class="box3">box3</div>
</body>
</html>